The individual water well systems with which this invention is concerned have intermittent flow and involve limited water consumption, in most cases amounting to up to no more than about 1500 gallons of water per day (i.e., in 24 hours). Such systems comprise in essence, a tank, a pump for delivering water from the well into the tank, and piping or like means for conducting water from the tank to selected locations. Because of the intermittent flow and small daily water usage in such systems, the pump which is used to pump the water into the tank is also utilized to compress the air trapped within the headspace in the tank above the water level. This compressed headspace air acts in the manner of a compressed spring and thus provides the force that drives the water through the piping system.
The "on/off" operation of the water well system is controlled by a pressure switch which is preset at a low pressure "on" and a higher pressure "off". In a 42-gallon tank the "on" setting is typically 20 to 30 psi so that when the pressure within the tank reaches such preset value, the pump is activated and additional water is pumped into the tank until the pressure reaches the preset "off" setting, typically somewhere in the range of 40 to 60 psi. As the water within the tank is drawn down, the air space is increased and accordingly, the pressure within the tank is reduced. The draw down volumes are not directly proportional to the pressure changes and therefore the higher "cut-in" and "cut-off" pressure limit switches may be preferred.
Unfortunately, in operation, systems of this type possess drawbacks and shortcomings. Air is water soluble. Moreover, when air and water are contained under pressure within a common container, the water will dissolve a greater quantity of air than it would at the same temperature under atmospheric pressure. Likewise, a reduction in temperature can also cause an increase in the volume of air absorbed or dissolved by the water.
The air absorbed by the water constitutes an air loss that occurs gradually over a period of time, and is governed to some extent by the water usage. As the air is absorbed, the water level in the storage tank continues to rise, which at the same time reduces the volume of water pumped into the tank per pump cycle (i.e., between the time the pump is activated and the time it is shut off). This can continue until such time as a draw down of, say, one gallon or less will cause a pump cycle. In typical 42-gallon systems, with an air/water volume ratio of 1:1, the pump will cycle on a 7.8 gallon draw down. Thus, for a 300 gallon per day water consumption, the standard 1:1 ratio computes into 40 pump cycles per day. On the other hand, if the tank becomes water-logged because of air absorption so that the pump delivers only one gallon per pump cycle, the pump would cycle 300 times per day. Consequently, the absorption of the air within the tank and resultant water-logging of the tank can, and often does, cause the pump to switch on and off to an excessive extent. This in turn results in excessive power consumption and wear and tear on the pump and its associated motor, to say nothing of the nuisance to the occupants of the dwelling of such frequent stops and starts of the motorized pump.
Heretofore systems have been devised to remedy this situation. However, such systems do not always measure up to the job for which they are intended. For example, some prior systems have employed apparatus which includes diaphragms which tend to deteriorate on aging. Also, some prior systems are incapable of delivering sufficient air to the storage tank to achieve optimal performance of the system. Other prior systems involving float control valves have been found on occasion to release air from the tank when there is actually a need to retain or increase the volume of air within the tank. Undue expense is still another shortcoming of some prior systems.
A need thus exists for an efficient, durable and economical system for overcoming these problems associated with the operation of individual water well systems so that the pump will not be caused to operate with excessive frequency, or worse yet, to fail.